1. Field of the Invention
The present invention relates to a multishaft index table using a plurality of worms.
2. Description of Prior Art
A multishaft index table generally has a plurality of worms arranged in series in a drive shaft in its axial direction, a gear-shaped rotation transmitting member for receiving the rotation of at least one motor disposed in the drive shaft, and a worm wheel meshed with each worm.
Such a multishaft index table rotates the drive shaft when the rotation transmitting member receives the rotation of the motors to synchronously rotate the worms by the drive shaft, thereby synchronously rotating the worm wheels and synchronously rotating the table coupled with the worm wheels.
In some of such index tables, each worm and a drive shaft portion are integrally produced and each drive shaft portion is connected with an adjacent drive shaft portion by a coupler to form a drive shaft, and in others of such index tables, worms and drive shafts are separately produced and the worms are coupled with the drive shafts by couplers such as keys or combining members.
In either of the above-mentioned multishaft index tables, the rotation transmitting member is disposed at one end portion of the drive shaft and transmits the rotation of the motor to the one end portion of the drive shaft. Consequently, the drive shaft, rotated upon receipt of the rotation force of the rotation transmitting member at its one end portion, rotates a plurality of worms.
In the conventional multishaft index table mentioned above, however, the rotation of the motor is only transmitted to the one end portion of the drive shaft, so that, when the rotation starts, a load passing from a corresponding table through a worm wheel and a load such as machining thrust act on worms such that, the nearer the worms are to the placement of the rotation transmitting member, the earlier they are subjected to the loads.
For instance, the load from the worm wheel in the first shaft meshed with the first worm which is the nearest to the placement of the rotation transmitting member firstly acts on the first worm, and then the load from the worm wheel in the second shaft meshed with the second worm which is in the second nearest position to the placement of the rotation transmitting member acts on the second worm.
As a result, the first worm is distorted relative to the second worm, causing displacement in positioning of the first shaft and the second shaft, and causing distortion between adjoining worms to displace the rotational angle positions of adjoining worm wheels and to displace the tables connected therewith. The farther from the placement of the rotation transmitting member, the greater the displacement of the rotational angle position is.
An object of the present invention lies in enabling accurate positioning of a table of each shaft by controlling the influence of loads from other tables to the minimum.
The multishaft index table according to the present invention comprises: a drive shaft having a plurality of worms arranged in series in the axial direction; a plurality of worm wheels respectively meshed with the worms; at least one motor; and at least one rotation transmitting member which transmits the rotation of the motor, upon receipt thereof, to the drive shaft. The rotation transmitting member is disposed in at least one portion selected from a group including at least one of the drive shaft portions between adjoining worms, at least one end of the drive shaft portion and at least one of drive shaft portions between adjoining worms, and both end portions of the drive shaft.
The rotation of the motor is transmitted to the drive shaft through the rotation transmitting member disposed at positions close to the worms, and the rotation of the drive shaft is transmitted to the worm wheel through the worms. Consequently, when the motor rotates, the table connected with the worm wheel is rotated.
In the present invention, since at least one rotation transmitting member is disposed in a position close to each worm of the drive shaft, the rotation of the motor is transmitted to the position close to each worm, irrespectively of the placement of the worms in the axial direction of the drive shaft. Consequently, influence of a load due to jigs and machining thrust from other tables on each worm is controlled to the minimum, thereby enabling accurate positioning of each table.
The multishaft index table can further comprise an intermediate drive shaft where a first transmitting member for receiving the rotation of the motor and a second transmitting member for transmitting the rotation of the first transmitting member, upon receipt thereof, to the rotation transmitting member. With this, by using the intermediate drive shaft, a plurality of the second transmitting members can be used, so that the range where the rotation of the motor can be transmitted is widened, thereby enabling accurate positioning of more tables.
The above-mentioned rotation transmitting member, the first transmitting member and the second transmitting member can use either a gear or a belt pulley. Using a gear or a belt pulley simplifies the structure of a rotation transmitting route from the motor to the worm wheel and enables to produce the multishaft index table at a low cost. Using a belt is also effective to lower noise.